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Diethylbenzenes

Diethylbenzene (DEB) is any of three isomers with the formula C<sub>6</sub>H<sub>4</sub>(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub>. Each consists of a benzene ring and two ethyl substituents. The meta and para have the greater commercial significance. All are colorless solids.

Production and applications

Diethylbenzenes arise as side-products of the alkylation of benzene with ethylene, which can be described as two steps. The first step is the industrial route to ethylbenzene, which is produced on a large scale as a precursor to styrene.

C<sub>6</sub>H<sub>6</sub> + C<sub>2</sub>H<sub>4</sub> → C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>5</sub>

The diethylbenzene is an inadvertent side product.

C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>5</sub> + C<sub>2</sub>H<sub>4</sub> → C<sub>6</sub>H<sub>4</sub>(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub>

Using shape-selective zeolite catalysts, the para isomer can be produced in high selectivity.

Much diethylbenzene is recycled by transalkylation to give ethylbenzene:

C<sub>6</sub>H<sub>4</sub>(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub> + C<sub>6</sub>H<sub>6</sub> → 2 C<sub>6</sub>H<sub>5</sub>C<sub>2</sub>H<sub>5</sub>

Uses

Diethylbenzene is used in a mixture with methyl and/or ethyl biphenyls as a low temperature heat transfer fluid.

Diethylbenzene is dehydrogenated to give divinylbenzene (DVB):

C<sub>6</sub>H<sub>4</sub>(C<sub>2</sub>H<sub>5</sub>)<sub>2</sub> → C<sub>6</sub>H<sub>4</sub>(C<sub>2</sub>H<sub>3</sub>)<sub>2</sub> + 2 H<sub>2</sub>

DVB is used in the production of crosslinked polystyrene.

References